[Maxima-commits] [git] Maxima CAS branch master updated. branch-5_49-base-543-gc295b89a4

[tomasriker <tom...@us...>]

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- Log -----------------------------------------------------------------
commit c295b89a4305bda4012e07943084f14d1d3e312a
Author: David Scherfgen <d.s...@go...>
Date:   Wed May 27 22:49:49 2026 +0200

    Fix GCSQR (wrong formula for squaring complex number, called by GCFACTOR)
    
    The function GCSQR, which computes the square of a complex number R + %i * I,
    wrongly computed the real part of the result as R^2 + I^2, when it should be
    R^2 - I^2. This bug broke GCFACTOR for some numbers.
    
    This fixes bug #4623.

diff --git a/src/numth.lisp b/src/numth.lisp
index 70e351319..61fba4e22 100644
--- a/src/numth.lisp
+++ b/src/numth.lisp
@@ -277,7 +277,7 @@
    (let ((r (first a))
          (i (second a)))
      (declare (integer r i))
-     (list (+ (* r r) (* i i)) (ash (* r i) 1))))
+     (list (- (* r r) (* i i)) (ash (* r i) 1))))
 
 (defun gctime1 (a b)
   (gctimes (car a) (cadr a) (car b) (cadr b)))
diff --git a/tests/rtest_numth.mac b/tests/rtest_numth.mac
index 06c65ee0a..671a6fd6c 100644
--- a/tests/rtest_numth.mac
+++ b/tests/rtest_numth.mac
@@ -809,3 +809,16 @@ gcfactor (%i / 2);
  sublist (%%, lambda ([x], x # true)));
 [];
  */
+
+/* Bug #4623: "gcfactor(4), expand(%%) => -4" */
+
+create_list(is(a + %i * b = expand(gcfactor(a + %i * b))), a, makelist(i, i, -4, 4), b, makelist(i, i, -4, 4));
+[true, true, true, true, true, true, true, true, true,
+ true, true, true, true, true, true, true, true, true,
+ true, true, true, true, true, true, true, true, true,
+ true, true, true, true, true, true, true, true, true,
+ true, true, true, true, true, true, true, true, true,
+ true, true, true, true, true, true, true, true, true,
+ true, true, true, true, true, true, true, true, true,
+ true, true, true, true, true, true, true, true, true,
+ true, true, true, true, true, true, true, true, true];

-----------------------------------------------------------------------

Summary of changes:
 src/numth.lisp        |  2 +-
 tests/rtest_numth.mac | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)


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